1. Field of the Invention
The present invention relates generally to a solution-dropping nozzle device. More particularly, the invention relates to a solution-dropping nozzle device for thin-film coating treatments.
2. Description of Relevant Art
A variety of nozzle devices are widely employed for dropping a liquid such as a coating liquid containing a diffusion agent or a coating liquid for the formation of a metal oxide film or a photoresist on an object to be treated. For example, to coat a diffusion agent for semiconductors on a wafer in a production process such as for an IC or an LSI, with reference to FIG. 4 of the accompanying drawings, a wafer 51 is mounted on a spinner 50 and, while or after dropping a coating liquid containing a diffusion agent from a nozzle 52 onto the surface of the central part of the wafer 51, is spun thereby at a high speed so as to provide a uniform coating of the diffusion agent on the surface of the wafer 51 by virtue of the centrifugal force.
After dropping the coating liquid from the nozzle 52, a small amount of the coating liquid still remains on a peripheral portion 52a at the tip of the nozzle 52 due to, for example, the surface tension. With the lapse of time, the remaining coating liquid on the peripheral portion 52a, which is generally a solution consisting of a diffusion agent dissolved in a solvent such as an organic solvent, will have only its solvent evaporate, thus being gradually concentrated to finally have its solute, i.e., the diffusion agent, educed.
The coating liquid as thus concentrated may fall on the wafer, rendering the coating uneven and causing the production of sub-standard goods, with a considerable disadvantage to productivity.
Conventionally, in order to avoid such disadvantage, the fall of such concentrated liquid has been prevented by wiping the nozzle tip with a sponge, a cloth or a filter paper, for example, which may selectively be impregnated with a solvent. However, such conventional method must rely upon manual operations, thus causing problems with respect to mass production. Moreover, if the spacing between a nozzle and a spinner is relatively narrow, the wiping work is difficult, and foreign material may fall on the wafer surface. Furthermore, such conventional method generally prevents a coating step and preceding and subsequent steps thereof from being performed by a series of continuous operations, thus further impeding full automation of the production process.
The present invention effectively overcomes the foregoing problems and disadvantages attendant conventional techniques.